A colorful book to inspire and inform novice decorators

The Decorating Book, by Mary Gilliatt. New York: Pantheon Books. $39.95. Sure you like minimalism, but a pair of director's chairs set off against the stark white walls of your new apartment is just a little too minimal. Or maybe your family room needs some imagination and a fresh color scheme to pull it together.

Whether you face the prospect with anticipation or a trembling paint brush, ''The Decorating Book,'' by English design consultant Mary Gilliatt, offers both information and inspiration. An ambitious project, the book organizes a vast amount of material into an inviting format full of color photographs. It covers the field from the general principles of design to the nuts and bolts of choosing bathroom fittings and lighting fixtures.

The book has a refreshing, non-elitist approach that encourages a beginner, armed with some basic knowlege and new ideas, to trust his or her instincts and plunge in. The author freely reveals trade secrets and reinforces the verity that creating a comfortable, functional, and appealing environment depends on more than just ''good taste.''

The opening section, ''Principles of Design,'' sets the ground rules for good decorating. It discusses efficient and creative use of space, ways to change a room structurally, how to visually expand or diminish a room, scale, furniture arrangements, the use of texture and pattern, and choosing a color scheme. This section also clarifies the tricky business of good lighting.

Almost half the book is devoted to the ''Room-by-Room Guide'' which gives design solutions for almost any kind of space, from a narrow studio apartment to a garden conservatory. Several examples of rooms are given under each of the umbrella categories which include entrance halls, living rooms, one-room living, dining rooms, bathrooms, kitchens, workrooms, and leisure rooms.

The first time through the ''Room by Room'' section is like leafing through the pages of House Beautiful, but a closer look reveals elements and ideas that can be adapted to many budget levels. Not many people have a magnificent farmhouse kitchen with the original thick beams and plastered walls, for example , but roughhewn furniture, strings of dried herbs, and wooden bowls filled with fruit can give the same effect in a less spectacular setting.

Each room is illustrated by a full-page color photo and renderings of two alternative versions. The individual components of furniture, lighting, flooring , woodwork, wall and ceiling materials are listed for each of the three schemes.

The Room-by-Room Guide is followed by a very useful section on paint, wallpaper, fabric, carpets and other floorings. The many choices currently available are illustrated by 96 pages of color samples with references to a directory of sources where they can be obtained, which is listed in the back of the book. The pages on Persian and other ethnic rugs are particularly vivid and eye-catching.

A furniture and furnishings section compounds the choices even more with a pictoral glossary of furniture types, staircases, doors, fireplaces and stoves, bathroom fixtures, storage ideas, and lighting. This allows the reader to think about the alternatives before shopping rather than scouting around stores to discover all the options.

For all the book's practicality, the finer points are not forgotten. A pleasing jumble of baskets hanging from the ceiling of a country kitchen, an array of plants set on glass shelves stretching across a window, a dark bronze-mirrored seascape gleaming in a bathroom, and tartan objects arranged on a painted chest, are just a few of the choice vignettes illustrating how important the finishing touches can be.

A ''design kit'' at the back of the book is set up to experiment with different furniture arrangements and color choices using the sample section, graph paper, and furniture cutouts provided in the book. Even if you are not inclined to cut and paste, this section will help you avoid costly mistakes by explaining how to draw up a set of priorities, a master worklist and a decorating timetable. It also discusses hiring contractors and, if you choose to do the work yourself, how to estimate quantities of paint, wallpaper, and floorings.

Although no book can guarantee no-fault success, ''The Decorating Book'' is a valuable resource you will turn to again and again.